Suunto A-30 NH Metric CompassSuunto A 30 is a reliable baseplate compass for navigating and surviving in extreme conditions. Depending on the variant, A 30 comes with Metric UTM scales and inch ruler or USGS UTM scales. The Earths magnetic field does not flow evenly between the magnetic poles along the surface of the planet. To compensate for the natural tilt in the magnetic field, Suunto compasses use one of two balancing systems and you should choose the variant best serving